We assessed the quality of center child care relationships with adults and peers for 414 children (ages 14 to 54 months). Classrooms were classified by ratio and group size provisions of the Federal Interagency Day Care Requirements (FIDCR) and by the Early Childhood and Infant and Toddler Environmental Rating Scales. Children cared for in classrooms meeting FIDCR ratios were more likely to be in classrooms rated as good or very good in caregiving and activities. Children in classrooms rated as good or very good in caregiving were more likely to be securely attached to teachers. Securely attached children were more competent with peers. Children cared for in classrooms meeting FIDCR group size were more likely to be in classrooms rated higher in activities. Children in classrooms rated high in activities were likely to orient to both adults and peers. Children with social orientations to adults and peers were more competent with peers.